276 



Journal of Agricultural Research 



Vol. XVI, No. 10 



that entered the surface had been retained within reach of the roots. 

 With forage crops like clover, where a still larger amount of moisture is 

 required for maximum yields, the same would hold true. 



Table XI. — Differences in moisture content of soil of plots j and 4 in season of igi8 



Date and depth of section. 



June II (1.82 inches of rain on June 8 to 10): 



I to 6 inches 



7 to 12 inches 



Second foot , 



Third foot 



June 26 (Only 0.15 inch of rain since June 10): 



I to 6 inches 



7 to 12 inches , 



July 18 (1.89 inches of rain on July 14-16, 2.78 inches 

 since June 26): 



I to 6 inches 



7 to 12 inches 



Second foot , 



Third foot 



Nov. 12 (2.32 inches of rain Nov. i to 8; 8.63 inches since 

 July 18): 



I to 6 inches 



7 to 12 inches 



Second foot 



Third foot 



Table XII. — Moistness of soil on plots in igi8 compared with that in igi 5, showing the 

 much drier condition of the subsoil in the former year 



Plot No. and depth of section. 



Ratios in igiS. 



June II. July 18. Nov. 12 



Ratios in 1915. 



July 7. Aug. 4. Sept. 2 



Plot 3: 



Firstfoot... 

 Second foot 

 Third foot. . 



Plot 4: 



Firstfoot... 

 Second foot 

 Third foot. . 



2.6 

 1.4 



I- 5 



2.7 



1-5 

 1-5 



2-5 



2.6 

 2.9 



2-S 

 2-5 



a. 9 



In general, it appears that percolation causes but little loss of the sum- 

 mer rainfall in the case of soils as fine in texture as the silt loams when 

 these are in grasses or small grains, the portion of the subsoil occupied by 

 the roots intercepting and giving up to the crop any of the moisture that 

 penetrates through the surface foot. On fields with a sharply rolling 

 surface a lowered water capacity, due to loss of organic matter, might be 

 accompanied also by greater difficulty of penetration, and hence by a 

 sufl&ciently greater loss by run-off to cause a markedly lower crop yield. 



